Set BLOCK_BIT_ERROR on bio submit failure during forced unmount

block_submit_bio will return -ENOLINK if called during a forced
shutdown, the bio is never submitted, and thus no completion callback
will fire to set BLOCK_BIT_ERROR. Any other task waiting for this
specific bp will end up waiting forever.

To fix, fall through to the existing block_end_io call on the
error path instead of returning directly.  That means moving
the forcing_unmount check past the setup calls so block_end_io's
bookkeeping stays balanced. block_end_io then sets BLOCK_BIT_ERROR
and wakes up waiters just as it would on a failed async completion.

Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/block.c

@@ -467,9 +467,6 @@ static int block_submit_bio(struct super_block *sb, struct block_private *bp,
 	sector_t sector;
 	int ret = 0;
 
-	if (scoutfs_forcing_unmount(sb))
-		return -ENOLINK;
-
 	sector = bp->bl.blkno << (SCOUTFS_BLOCK_LG_SHIFT - 9);
 
 	WARN_ON_ONCE(bp->bl.blkno == U64_MAX);
@@ -480,6 +477,17 @@ static int block_submit_bio(struct super_block *sb, struct block_private *bp,
 	set_bit(BLOCK_BIT_IO_BUSY, &bp->bits);
 	block_get(bp);
 
+	/*
+	 * A second thread may already be waiting on this block's completion
+	 * after this thread won the race to submit the block.  We exit through
+	 * the block_end_io error path which sets BLOCK_BIT_ERROR and assures
+	 * that other callers in the waitq get woken up.
+	 */
+	if (scoutfs_forcing_unmount(sb)) {
+		ret = -ENOLINK;
+		goto end_io;
+	}
+
 	blk_start_plug(&plug);
 
 	for (off = 0; off < SCOUTFS_BLOCK_LG_SIZE; off += PAGE_SIZE) {
@@ -517,6 +525,7 @@ static int block_submit_bio(struct super_block *sb, struct block_private *bp,
 
 	blk_finish_plug(&plug);
 
+end_io:
 	/* let racing end_io know we're done */
 	block_end_io(sb, opf, bp, ret);
 

kmod/src/quota.c

@@ -34,6 +34,7 @@
 #include "totl.h"
 #include "util.h"
 #include "quota.h"
+#include "trans.h"
 #include "counters.h"
 #include "scoutfs_trace.h"
 
@@ -1086,6 +1087,10 @@ int scoutfs_quota_mod_rule(struct super_block *sb, bool is_add,
 	if (ret < 0)
 		goto out;
 
+	ret = scoutfs_hold_trans(sb, true);
+	if (ret < 0)
+		goto out;
+
 	down_write(&qtinf->rwsem);
 
 	if (is_add) {
@@ -1095,28 +1100,30 @@ int scoutfs_quota_mod_rule(struct super_block *sb, bool is_add,
 		else if (ret == 0)
 			ret = -EEXIST;
 		if (ret < 0)
-			goto unlock;
+			goto release;
 
 		rule_to_rule_val(&rv, &rule);
 		ret = scoutfs_item_create(sb, &key, &rv, sizeof(rv), lock);
 		if (ret < 0)
-			goto unlock;
+			goto release;
 
 	} else {
 		ret = find_rule(sb, &rule, &key, lock) ?:
 		      scoutfs_item_delete(sb, &key, lock);
 		if (ret < 0)
-			goto unlock;
+			goto release;
 	}
 
 	scoutfs_quota_invalidate(sb);
 	ret = 0;
 
-unlock:
+release:
 	up_write(&qtinf->rwsem);
-	scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
+	scoutfs_release_trans(sb);
 
 out:
+	scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
+
 	if (is_add)
 		trace_scoutfs_quota_add_rule(sb, &rule, ret);
 	else

tests/funcs/filter.sh

@@ -87,7 +87,7 @@ awk '
 	( in_block == 2 ) {
 		buf = buf $0 "\n"
 		if ($0 ~ /<\/TASK>/) {
-			if (buf ~ /xfs_nondir_ilock_class/ && buf ~ /fs_reclaim/) {
+			if (buf ~ /xfs_(nondir_|dir_)?ilock_class/ && buf ~ /fs_reclaim/) {
 				# known xfs lockdep false positive, discard
 			} else {
 				printf "%s", buf

tests/run-tests.sh

@@ -694,8 +694,8 @@ for t in $tests; do
 		if [ "$sts" == "$T_PASS_STATUS" ]; then
 			dmesg | t_filter_dmesg > "$T_TMPDIR/dmesg.after"
 			diff --old-line-format="" --unchanged-line-format="" \
-				"$T_TMPDIR/dmesg.before" "$T_TMPDIR/dmesg.after" > \
-				"$T_TMPDIR/dmesg.new"
+				"$T_TMPDIR/dmesg.before" "$T_TMPDIR/dmesg.after" | \
+				grep -v '^$' > "$T_TMPDIR/dmesg.new"
 
 			if [ -s "$T_TMPDIR/dmesg.new" ]; then
 				message="unexpected messages in dmesg"